Internal combustion engine dual induction system

ABSTRACT

An internal combustion engine having a cylinder head positioned over the end of a combustion chamber with the cylinder head having primary and secondary induction passages positioned therein. An induction valve, including a valve stem and a valve head, is reciprocably mounted within the cylinder head and a tube is preferably press fitted in a bore in the cylinder head. The primary induction passage communicates with the exterior of this tube and the secondary passage communicates with the interior of the tube. This tube extends to a position closely adjacent to, or in engagement with, the head of the induction valve when the valve is in the closed position, thereby providing a good seal between the primary and secondary induction passages when the induction valve is closed.

United States Patent Diehl 51 July 25,1972

INTERNAL COMBUSTION ENGINE DUAL INDUCTION SYSTEM Inventor: Roy E. Diehl,Livonia, Mich.

Assignee: Ford Motor Company, Dearborn, Mich.

Filed: June 29, 1970 Appl. No.: 50,619

U.S.Cl ..123/52 M, 123/188 M, 123/188 S, 123/52 MV, 123/75 B Int. Cl..F02b 75/18, F011 3/00, F02b 75/02 FieldofSearch ..123/188 M, 188 5,52MV,52 M, 123/75 B, 127 R References Cited UNITED STATES PATENTSSchumacher ..123/188 S FOREIGN PATENTS OR APPLICATIONS 338,559 11/1930Great Britain ..123/75 B Primary ExaminerWendel1 E. Burns AssistantExaminer-A. M. Zupcic Al!0rney--.lohn R. Faulkner and Keith L.Zerschling [57] ABSTRACT An internal combustion engine having a cylinderhead positioned over the end of a combustion chamber with the cylinderhead having primary and secondary induction passages positioned therein.An induction valve, including a valve stem and a valve head, isreciprocably mounted within the cylinder head and a tube is preferablypress fitted in a bore in the cylinder head. The primary inductionpassage communicates with the exterior of this tube and the secondarypassage communicates with the interior of the tube. This tube extends toa position closely adjacent to, or in engagement with, the head of theinduction valve when the valve is in the closed position, therebyproviding a good seal between the primary and secondary inductionpassages when the induction valve is closed.

10 Claims, 5 Drawing Figures Patented July 25, 1972 3,678,905

3 Sheets-Sheet 1 Q, gt AfRNEYQ INVENTOR 4? 0/544 Patentod July 25, 1912v $678,905

3 Sheets-Sheet 2 l NVENTOR BY I 7 W a? ATTORN S Patentod July 25, 19723,678,905

INVENTOR R0) 4 0/544 wa y/2 ATTORN YS INTERNAL COMBUSTION ENGINE DUALINDUCTION SYSIEM BACKGROUND OF THE INVENTION This invention relatesgenerally to air-fuel induction systems for internal combustion enginesand, more particularly, to an internal combustion engine having primaryand secondary induction passages leading to an intake valve of acombustion chamber.

Dual induction systems for internal combustion engines including dualinduction intake passages and ports for the combustion chambers ofinternal combustion engines are known in the art. These dual inductionsystems include a small primary passage communicating with a carburetorand an intake or induction valve in a combustion chamber and a largersecondary air or air-fuel passage also communicating with the intake orinduction valve. In these systems, an air-fuel mixture for engineoperation at idle and at normal road loads is supplied from thecarburetor of the internal combustion engine to the combustion chambersthrough the small primary air-fuel passages and a second air-fuelmixture, or excess air, is supplied to the combustion chambers throughmuch larger secondary air passages when the internal combustion engineis operating under very high load conditions, such as those that occurduring peak acceleration periods and at wide open throttle.

These dual induction systems have several advantages over theconventional single induction systems currently used in internalcombustion engines that employ a single induction passage leading fromthe carburetor to an intake valve located in a combustion chamber. Atidle and normal road loads, the air flow through the small primaryinduction passages has a velocity sufficient to fully mix the fuel withthe air and to supply all of the combustion chambers of the internalcombustion engine with substantially the same air-fuel mixtures. Thisaction results in more complete burning of the fuel in each combustionchamber of the internal combustion engine thereby resulting in betterengine operation and a reduction in the unburned hydrocarbons and carbonmonoxide emitted by the internal combustion engine.

In order to maximize the above mentioned advantages of a dual inductionsystem, it is necessary that the primary air-fuel passage and thesecondary air-fuel or air passage be fully separated and sealed from oneanother to form complete and separate passages when the intake valve isclosed. If this is not the case, as is true in many of the prior artdevices, the air-fuel mixture flowing through the primary inductionpassage will feed back through the secondary air-fuel or air passage tothe other combustion chambers of the engine thereby reducing thevelocity of flow through the primary air-fuel passage and reducing thevelocity of the air-fuel mixture in the primary passage. This reducesthe magnitude of the advantages brought out above, i.e. it will resultin a less even air-fuel mixture for each of the cylinders or combustionchambers and it will reduce smoothness of engine operation, as well as,increasing the amount of unburned hydrocarbons and carbon monoxideemitted from the internal combustion engine.

In other words, for a dual induction passage system to function at topefficiency and at its optimum performance levels, a good, if not airtight, seal is necessary between the primary airfuel passage and thesecondary air-fuel or air passage when the intake or induction valve isclosed. The present invention pro vides a feasible, economical andeasily constructed dual induction construction for an internalcombustion engine in which such a seal is provided.

SUMMARY OF THE INVENTION This invention includes a combustion chamber inan internal combustion engine having a piston reciprocably mountedtherein. A cylinder head is positioned over one end of the combustionchamber and primary and secondary induction passages are positioned inthe cylinder head. As is conventional, the induction valve has a valvestem and a valve head and the valve stem is reciprocably mounted withinthe cylinder head. The cylinder head has a bore positioned therein whichpreferably has a diameter slightly less than the diameter of the valveseat that receives the valve head. A tube or cylinder is positioned inthis bore, preferably in a press fit relationship, and one end of thistube is positioned closely adjacent to, and preferably in direct contactwith, the head of the valve when the induction valve is in a closedposition.

The primary induction passage that carries an air-fuel mixture duringidle and nonnal load conditions of the internal combustion enginecommunicates with the exterior of this tube, preferably with a toroidalshaped passage positioned around the exterior, and the secondaryair-fuel or air passage communicates with the interior of the tube.

As a result of the above construction, the primary air-fuel passage andthe secondary air-fuel or air passage are completely separated from oneanother when the induction valve is in a closed position. When theinduction valve opens, air-fuel mixture flows around the exterior of thecylinder or tube, preferably through the toroidal shaped passage, toprovide a swirling action for the air-fuel mixture and the secondaryair-fuel mixture or secondary air pours into the combustion chambersubstantially axially of the valve stem and within the swirling actionof the air-fuel mixture coming from the primary air-fuel passage. Thisaction provides good mixing of the fuel in the combustion chamber toaccomplish complete combustion and burning of the hydrocarbons containedin the fuel.

As stated above, the cylinder or tube is preferably press fitted withinthe bore surrounding the valve stem. As a result, the end of the tubeadjacent the valve head may be positioned in engagement therewith toprovide a complete seal between the primary air-fuel passage and thesecondary air-fuel or air passage. When the valve face on the valve headand the valve seat wear so that the valve head progresses further intothe cylinder head during normal wearing conditions, the head will strikethe end of the cylinder or tube and drive it further within the bore. Asa result, the clearance between the valve head and the end of thecylinder or tube adjacent to it will be maintained at or close to zeroover the whole operating life of the internal combustion engine.

With a good seal provided between the primary air-fuel passage and thesecondary air-fuel or air passage, the velocities of the air-fuelmixture in the primary passages can be maintained at a high level. As aresult, the air-fuel ratios supplied to each combustion chamber will besubstantially the same thereby preventing overly rich mixtures frombeing supplied to certain combustion chambers and very leanuncombustible mixtures from being supplied to others. This alone willresult in the lowering of unburned hydrocarbon emissions. In addition,the air-fuel mixtures supplied to the primary airfuel passages can beset at high levels, for example, 17 -l at idle and 20 1 during part loadoperating conditions. With these high air-fuel ratios, the hydrocarbonsin the fuel will be burned more thoroughly thereby resulting in lowunburned hydrocarbon emissions. In addition, with the high ratio of airin the combustion chambers, low levels of carbon monoxide emissions willresult. Moreover, the large amount of air supplied to the combustionchambers will reduce the temperatures of combustion thereby resulting inlower emission levels of oxides of nitrogen.

in the preferred embodiment of the invention, the bore in the cylinderhead that receives the valve stem, the valve seat that receives thesealing face of the valve head, and the bore that receives the cylinderor tube are all co-axially aligned. As a result, after castingoperations of the head are complete, a single milling operation with amilling cutter having a multiple of milling surfaces may be employed tomachine the two bores and the valve seat in the cylinder head. The onlyremaining operation necessary is to press fit the tube or cylinder intothe bore in the cylinder head.

An object of the present invention is the provision of a dual inductionsystem for an internal combustion engine which is effective to reduceundesirable gaseous emissions from the internal combustion engine.

Another object of the invention is the provision of a dual inductionsystem providing a complete seal between the primary air-fuel passageand the secondary air-fuel or air passage which is inexpensive, easy tofabricate, and is effective over the complete operating life of theengine.

Other objects and attendant advantages of the present invention willbecome more readily apparent as the drawings are considered inconnection with the specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view through theintake manifold and a portion of the cylinder head of an internalcombustion engine employing the present invention;

FIG. 2 is a sectional view, partially in elevation, through a combustionchamber of an internal combustion engine employing the present inventionand showing the induction valve in the closed position;

FIG. 3 is a partial section view similar to FIG. 2 and showing theinduction valve in the open position;

FIG. 4 is a sectional view along the lines 44 of FIG. 2; and

FIG. 5 is a sectional viewtaken along the lines 5-5 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,in which like reference numerals designate like parts throughout theseveral view thereof, there is shown in FIG. 1 an induction manifoldwhich has a primary air-fuel passage 12 and a larger, secondary air-fuelor air passage 14 located therein. As shown here in outline form, acarburetor 16 having a throttle valve 18 is employed to feed an air-fuelmixture via tube 20 into the primary air-fuel passage 12. Additionally,a portion of this carburetor, for example, a portion of a conventionalfour-barrel carburetor having a throttle valve 22, is employed to feedan air-fuel mixture into the secondary air-fuel passage 14. Although thepresent invention is illustrated with a carburetion system including thethrottle valve 22 for feeding an air-fuel mixture into the secondaryair-fuel passage 14, the invention also may be employed with ,a systemin which air only is fed into the secondary air passage 14 under thecontrol of throttle valve 22.

The induction manifold 10 is connected to a cylinder head 24 at theleft-hand side, as viewed in FIG. 1, and may be similarly connected, inthe case of a V-type engine, with a similar cylinder head 26 located atthe right-hand side of FIG. 1. 1

The invention will be described in connection with a single combustionchamber, as shown in FIG. 2 and as partially shown in FIG. 1. It is tobe understood, however, that each combustion chamber in the internalcombustion engine is identical.

The cylinder head 24 includes a primary air-fuel induction passage 28that communicates with the primary air-fuel passage 12 located in theinduction manifold 10. It also includes a secondary air-fuel or airinduction passage 30 that communicates with the secondary air-fuel orair passage 14 located in the induction manifold 10. The primaryair-fuel passage 28 and the secondary air-fuel or air passage 30terminate at an induction valve 32 havinga stem 34 reciprocably mountedwithin a bore 36 in the cylinder head 24 and a valve head 38 having avalve face 40 which is adapted to seat in sealing engagement with avalve seat 42 positioned in the cylinder head 24.

As shown in FIG. 2, the cylinder head 24 is positioned over a cylinderblock 44 of the internal combustion engine which has an internal bore orcylinder 46 for receiving a reciprocably mounted piston 48 therebyforming a combustion chamber 50. The cylinder head 24 also has mountedtherein a conventional spark plug 52 which is employed to ignite thefuel-air mixture admitted into the combustion chamber 50 when theinduction valve 32 is opened.

The cylinder head 24 is provided with an induction chamber 53 having abore or opening 54 located axially intermediate the bore 36 thatreceives the valve stem 34 and the valve seat 42. This bore ispreferably co-axially positioned with respect to the bore 36 and thevalve seat 42 and it receives a tube or cylinder 56. One end 58 of thecylinder or tube 56 terminates in the secondary air-fuel or air passage30 while the other end 60 terminates closely adjacent to or inengagement with the valve head 38. The cylinder or tube 56 is preferablypress fitted within the bore 54 and the end 60 preferably ispositionedin engagement with the valve head 30 when the valve 32 is in the closedposition, as shown in FIGS. 1 and 2. In other words, there is preferablya zero clearance between the end 60 of the tube or cylinder 56 and thevalve head 38 when the valve 32 is closed, as shown in these twofigures.

As can be readily appreciated by an inspection of FIGS. 2, 4 and 5, theprimary air-fuel passage 28 and the secondary airfuel or air passage 30positioned in the cylinder head 24 are separated and sealed from oneanother when the valve 32 is in the closed position, as shown.

Referring now to FIGS. 2, 4 and 5, it can be seen that the secondaryair-fuel or air passage 30 communicates directly with theinterior of thetube or cylinder 56 at the end 58 thereof. On the other hand, theprimary air-fuel passage 28 communicates with the exterior of thecylinder or tube 56 via a toroidal shaped passage 62 positioned in thecylinder head 24 intermediate the bore 54 and the valve seat 42 in anaxial direction, as best shown in FIGS. 1 and 2. This toroidal shapedpassage 62 extends around the tube 56 and preferably includes aprotuberance 64 positioned therein and forming part of the cylinder head24. This protuberance 64 serves as a restriction for the air-fuelmixture flowing in the primary airfuel passage 28 so that the path ofthe air-fuel mixture in the toroidal passage 62 is in a counterclockwisedirection, as viewed in FIG. 5.

As a result of the above structure, when the induction valve 32 opens asshown in FIG. 3, the air-fuel mixture flowing through the primaryair-fuel passage 28 and in a swirling path through the toroidal shapedpassage 62 is drawn into the combustion chamber 50 in a swirling action.On the other hand, the air-fuel mixture or air flowing through thesecondary airfuel or air passage 30- is drawn into the combustionchamber 50 through the interior of the cylinder or tube 56 and entersthe combustion chamber 50 in substantially co-axial relationship to theswirling fuel drawn into the combustion chamber from the primaryair-fuel passage 28 and the toroidal shaped passage 62. This providesfor a thorough mixing of the air-fuel mixture flowing through theprimary air-fuel passage 28 and toroidal passage 62 and the air-fuelmixture or excess air flowing in the secondary air-fuel passage or airpassage 30. As a result of this complete mixture, more thorough andcomplete burning of the fuel is accomplished.

In the construction of the cylinder head of the present invention, theprimary air-fuel passages 28 and the secondary air-fuel or air passages30 are cast together with the chambers 53, as shown in FIGS. 1 and 2,that have the bores 36 and 54 and the valve seat 42 located therein. Thebores 36 and 54, as well as, the valve seat 42 may be machined in thecylinder head 24 by means of a single milling cutter having a multipleof milling faces. This is true because in the preferred embodiment ofthe invention, the bores 36 and 54 and the valve seat 42 are positionedin the cylinder head 24 in co-axially aligned relationship. The cylinderor tube 56 may then be press fitted in the bore 54 and into a positionwhere the end 60 will have very minimal clearance and preferably zeroclearance with respect to the valve head 38 of the induction valve 32when the valve is closed, as shown in FIGS. 1 and 2.

In internal combustion engines, the valve seat 42 positioned in thecylinder head 24, as well as, the valve face 40 positioned on the valvehead 38 wear during normal operations so that the valve 32 in the closedposition extends farther and farther into the cylinder head 24 oraxially upwardly, as viewed in FIGS. 1 and 2. When this occurs, thevalve head 38 will strike the end 60 of the tube or cylinder 54 and willdrive the cylinder or tube 54 axially upwardly, as viewed in FIGS. 1 and2, to maintain the zero clearance between the end 60 of the tube 54 andthe valve head 30. This may be accomplished since the tube or cylinder56 is originally press fitted within the bore 54.

The tube or cylinder 56 will operate at zero clearance with respect tothe valve head 38 when the induction valve 32 is closed throughout theoperating life of the engine and will provide a complete seal betweenthe primary air-fuel passage 28 and the secondary air-fuel or airpassage 30 throughout the operating life of the internal combustionengine. As a result of this seal, there will be no feedback of theair-fuel mixture in the primary air-fuel induction passages 28 throughthe secondary air-fuel or air passages 30 and the secondary air-fuel orair passages 14 in induction manifold from combustion chambers in whichinduction valves are closed to chambers in which the induction valvesare open. The velocity of air-fuel mixture in the primary air-fuelpassages 28, therefore, will be maintained at all times at optimum anddesign levels. Each combustion chamber 50 will receive a thoroughlymixed airfuel mixture having substantially the same air-fuel ratioduring idle and part load conditions. Consequently, it is possible tooperate the internal combustion engine with large air-fuel ratios. Thislarge amount of air, together with the complete mixing of the fuel,results in more complete burning of the fuel thereby lowering emissionlevels of unburned hydrocarbons and carbon monoxide. The large amount ofair also reduces the temperatures of combustion thereby lowering theemission levels of oxides of nitrogen.

Thus, the present invention provides a dual induction system for acombustion chamber of an internal combustion engine that is easily andinexpensively constructed, and that provides complete sealing actionbetween the primary air-fuel passage and the secondary air-fuel or airpassage of the induction system throughout the operating life of theinternal combustion engine. This results in a highly efficient andeffective dual induction system that reduces the emission levels ofundesirable products of combustion generated in the internal combustionengine.

I claim:

1. An internal combustion engine comprising a combustion chamber, acylinder head positioned over one end of said chamber, an inductionvalve mounted in said cylinder head for reciprocable movement therein,said induction valve including a stem and a head having a face, saidcylinder head having a bore positioned therein receiving said stem and avalve seat receiving said face, said stem and valve seat beingpositioned co-axially with respect to each other, said cylinder headhaving a primary inductionpassage and a secondary induction passagelocated therein and a second chamber positioned therein around said stemof said valve, said second chamber including a second bore locatedco-axially with respect to the bore receiving said stem of said valveand with respect to said valve seat, a cylindrical tube press fitted insaid second bore in said second chamber, said secondary inductionpassage being in communication with one end of said tube, the other endof said tube being in engagement with the head of said valve when saidvalve face is positioned against said valve seat, the primary inductionpassage communicating with the exterior of said tube, said cylindricaltube being incrementally displaceable relative to said second bore toaccommodate for wear of said valve head face and said valve seat.

2. An internal combustion engine comprising a combustion chamber havinga piston reciprocably mounted therein, a cylinderhead positioned overone end of said combustion chamber, said cylinder head having a primaryinduction passage and a secondary induction passage, an induction valvehaving a valve stem and a valve head, said induction valve beingreciprocably mounted in said cylinder head, said cylinder head having abore positioned therein, a tube press fitted in said bore and extendingto a position at one end in engagement with the head of said valve whensaid valve is in a closed position, said secondary passage communicatingwith the interior of said tube and said primary induction passagecommunicating with the exterior of said tube, the opening of saidprimary induction passage to the combustion chamber being locatedoutside of said tube, the opening of said secondary induction passage tothe combustion chamber being located within said tube, said tube beingincrementally displaceable relative to said bore to accommodate for wearof engagable portions of said valve head and said cylinder head.

3. The combination of claim 2 in which said cylinder head has a borepositioned therein for receiving said valve stem and a valve seat forreceiving said valve head, said bore for receiving said valve stem andsaid bore receiving said tube and said valve seat being co-axial.

4. The combination of claim 3 in which thebore receiving said tube andsaid tube are of smaller diameter than the diameter of said valve seat.

5. The combination of claim 3 in which said bore receiving said tube islocated axially intermediate said bore in said cylinder head receivingsaid valve stem and said valve seat, the other end of said tubeterminating at the end of said bore adjacent said bore in said cylinderhead receiving said valve stem.

6. In an internal combustion engine having structural means defining acombustion chamber,

a piston reciprocably positioned therein,

an induction valve reciprocably mounted in said structural means,

said structural means having a second chamber positioned therein aroundsaid induction valve and a primary induction passage and a secondaryinduction passage located therein,

a bore formed in said chamber a cylindrical tube press fitted in saidbore and extending axially into engagement with said valve head whensaid valve head is seated on said valve seat, the interior of said tubecommunicating with said secondary induction passage and the exterior ofsaid tube communicating with the secondary induction passage, saidcylindrical tube being incrementally displaceable relative to said boreto accommodate for wear of engagable portions of said induction valveand said second chamber.

7. The combination of claim 6 in which said primary induction passageincludes a toroidal shaped passage positioned around the exterior ofsaid cylindrical tube.

8. A dual induction intake port foran internal combustion enginecomprising,

a cylinder head, said cylinder head having a chamber,

a first induction passage,

and a second induction passage positioned therein,

said chamber having a bore positioned in one end thereof,

and a valve seat at the other end thereof,

an induction valve having a valve stem and a valve head, said valve stempositioned in said bore and said valve head adapted to seat against saidvalve seat when said valve is in a closed position,

said chamber having a second bore positioned intermediate said firstmentioned bore and said valve seat,

a cylindrical tube press fitted in said second bore and extending fromsaid second bore to a position engagable with said valve head when saidinduction valve is in a closed position,

said first induction passage communicating with the interior of saidcylindrical tube and said second induction passage communicating withthe exterior of said cylindrical tube,

said cylindrical tube being incrementally displaceable relative to saidsecond bore to accommodate for wear of said valve head and said valveseat.

9. The combination of claim 8 in which said first and second bores, saidcylindrical tube and said valve seat are co-axial.

10. The combination of claim 9 in which said cylindrical tube and saidsecond bore have diameters smaller than said valve seat and said valvestem extends through said cylindrical tube in co-axial spacedrelationship.

1. An internal combustion engine comprising a combustion chamber, acylinder head positioned over one end of said chamber, an inductionvalve mounted in said cylinder head for reciprocable movement therein,said induction valve including a stem and a head having a face, saidcylinder head having a bore positioned therein receiving said stem and avalve seat receiving said face, said stem and valve seat beingpositioned co-axially with respect to each other, said cylinder headhaving a primary induction passage and a secondary induction passagelocated therein and a second chamber positioned therein around said stemof said valve, said second chamber including a second bore locatedco-axially with respect to the bore receiving said stem of said valveand with respect to said valve seat, a cylindrical tube press fitted insaid second bore in said second chamber, said secondary inductionpassage being in communication with one end of said tube, the other endof said tube being in engagement with the head of said valve when saidvalve face is positioned against said valve seat, the primary inductionpassage communicating with the exterior of said tube, said cylindricaltube being incrementally displaceable relative to said second bore toaccommodate for wear of said valve head face and said valve seat.
 2. Aninternal combustion engine comprising a combustion chamber having apiston reciprocably mounted therein, a cylinder head positioned over oneend of said combustion chamber, said cylinder head having a primaryinduction passage and a secondary induction passage, an induction valvehaving a valve stem and a valve head, said induction valve beingreciprocably mounted in said cylinder head, said cylinder head having abore positioned therein, a tube press fitted in said bore and extendingto a position at one end in engagement with the head of said valve whensaid valve is in a closed position, said secondary passage communicatingwith the interior of said tube and said primary induction passagecommunicating with the exterior of said tube, the opening of saidprimary induction passage to the combustion chamber being locatedoutside of said tube, the opening of said secondary induction passage tothe combustion chamber being located within said tube, said tube beingincrementally displaceable relative to said bore to accommodate for wearof engagable portions of said valve head and said cylinder head.
 3. Thecombination of claim 2 in which said cylinder head has a bore positionedtherein for receiving said valve stem and a valve seat for receivingsaid valve head, said bore for receiving said valve stem and said borereceiving said tube and said valve seat being co-axial.
 4. Thecombination of claim 3 in which the bore receiving said tube and saidtube are of smaller diameter than the diameter of said valve seat. 5.The combination of claim 3 in which said bore receiving said tube islocated axially intermediate said bore in said cylinder head receivingsaid valve stem and said valve seat, the other end of said tubeterminating at the end of said bore adjacent said bore in said cylinderhead receiving said valve stem.
 6. In an internal combustion enginehaving structural means defining a combustion chamber, a pistonreciprocably positioned therein, an induction valve reciprocably mountedin said structural means, said structural means having a second chamberpositioned therein around said induction valve and a primary inductionpassage and a secondary induction passage located therein, a bore formedin said chamber a cylindrical tube press fitted in said bore andextending axially into engagement with said valve head when said valveheaD is seated on said valve seat, the interior of said tubecommunicating with said secondary induction passage and the exterior ofsaid tube communicating with the secondary induction passage, saidcylindrical tube being incrementally displaceable relative to said boreto accommodate for wear of engagable portions of said induction valveand said second chamber.
 7. The combination of claim 6 in which saidprimary induction passage includes a toroidal shaped passage positionedaround the exterior of said cylindrical tube.
 8. A dual induction intakeport for an internal combustion engine comprising, a cylinder head, saidcylinder head having a chamber, a first induction passage, and a secondinduction passage positioned therein, said chamber having a borepositioned in one end thereof, and a valve seat at the other endthereof, an induction valve having a valve stem and a valve head, saidvalve stem positioned in said bore and said valve head adapted to seatagainst said valve seat when said valve is in a closed position, saidchamber having a second bore positioned intermediate said firstmentioned bore and said valve seat, a cylindrical tube press fitted insaid second bore and extending from said second bore to a positionengagable with said valve head when said induction valve is in a closedposition, said first induction passage communicating with the interiorof said cylindrical tube and said second induction passage communicatingwith the exterior of said cylindrical tube, said cylindrical tube beingincrementally displaceable relative to said second bore to accommodatefor wear of said valve head and said valve seat.
 9. The combination ofclaim 8 in which said first and second bores, said cylindrical tube andsaid valve seat are co-axial.
 10. The combination of claim 9 in whichsaid cylindrical tube and said second bore have diameters smaller thansaid valve seat and said valve stem extends through said cylindricaltube in co-axial spaced relationship.